Magnetite nanosized particles synthesis was achieved by two different routes. Assessment of microstructure was carried out aiming at comparing the outcome of synthesis parameters on the crystallinity, distribution of particle dimension and magnetic activity of nanosized particles precipitated in aqueous solution. Increasing of the nanoparticles crystallite size by stirring could be evidenced by the results. Temperature does not significantly affect crystallite size and crystallinity. The type of precursor was the factor that most contributed to the definition of crystallinity and particle size distribution. The route which used FeSO 4 .7H 2 O as precursor favored large crystallite sizes and crystallinity, while the route which used Fe 2 SO 4 .7H 2 O and FeCl 3 .6H 2 O as precursors resulted in much smaller crystallite sizes and crystallinity.